No it won't. I tried this before out of curiosity and for experimentation, and found that the spray foam just never gets solid enough or dense enough to do the job. It may be ok to insulate your windows and doors, but not to lengthen or otherwise alter a form. Stick with the two part foam for that.

Any one know if two part foam is available at a retail store of any kind or just from the supply companies? And when you say it's not dense enough what do you mean? It just dosn't get as firm as two part foam? What exactly is it that won't work about it? Just that it's to soft?

I have used spray foam for putting back together coyotes and on fish heads and none of the heads have fallen off or the coyote hasent broken in two i have had good luck with it

Double Bull, she is not talking about just putting the form together for which the spray foam probably works, she is talking about adding length to the form. For this the spray foam is unsuitable as it is not dense enough. She needs to get the two part foam for alterations of that kind.

Spray foam is what it's designed for, an insulator. It is a soft foam similar to the target foams and is not as staple as the two part foam. Remember, it activates when it contacts with air. There's no real chemical interaction going on.

NEXT question Jessica, however, is WHY do you need to lengthen your form. It always scares me when a beginner tells me he needs a form "lengthened. Many times it's a DP hide that is overstretched to begin with or a tanned hide that hasn't been stretched properly. If the eye nose are correct and the girth is correct,then the form is most likely correct. Anytime you lengthen a form you risk having a mount that looks disfigured. Be very careful and be very sure before you EVER just lengthen a form.

Thanks for all the tips. I don't like to consider myself a beginner any more but I do have alot more to learn. Thanks for all the tips on the spray foam, just excited about mounting the fawn and didn't want to wait for an order of foam to come. I have a pied fawn that I wanted to mount on the form, every other measurement is exact, the leg lengths, eye to nose, girth and neck but the nose to base of tail is about 4 inches different. I have the carcass from the fawn, just skinned it the other day, tanning it right now, so I know the measurements I have are correct. I measured like 15 times to make sure I was getting the right measurement. Both the form and the fawn look normal, so I'm not sure why there is such a big difference in the sizes on them. Any tips or help are much appreciated!

Jessica, if you attempt to stretch that fawn form 4 inches, it's going to look like a weasel. Remember, your fawn is dead and with death comes a natural relaxation of muscles and estention of disk joints in the spine. A skin is very VERY pliable and with the help of a good hide paste, you will be able to "pack" that hide proportionately over the length of the form. With a riffler file, cut your "bones" into the foam and just use an accordian effect. The neck skin will also "scrunch up" to shorten your measurement. If all those other measurements are that, there's no way I'd ever extend that form.